The last several years have seen an increasing amount of emphasis on designing engines more compactly and yet with improved fuel economy and efficiency, reduced emissions, greater service life, and an increased power output per cylinder. As present day engines are converted or upgraded, the piston assembly is subjected to even higher combustion chamber pressures and temperatures. Attempts have been made to overcome the effects of higher temperatures induced into pistons. One of the primary paths attempted has been to increase the efficiency of heat rejected from the piston crown. For example, many of today's high output engines employ cooling of the underside of the piston crown by spraying a cooling medium against the underside of the hot crown. The cooling medium absorbs a portion of the heat within the crown, falls away from the crown, is cooled and recycled to cool the piston crown again. To insure efficient cooling of the undercrown, the spray must be precisely directed to best remain in contact with the undercrown to absorb the heat therefrom.
U.S. Pat. No. 4,979,473 to Thomas R. Lee issued Dec. 25, 1990 discloses an example of a nozzle used to cool the underside of a piston. The nozzle includes a two piece assembly. The assembly includes a structural body attached to the engine and a formed tube having one end swedged forming an orifice and the other end attached to the body. The body includes a passage and a bore intersecting the passage. The end of the tube being attached to the body is positioned in the bore. Thus, the flow area between the two pieces of the assembly fail to provide a smooth efficient flow of cooling fluid
Another example of such a cooling arrangement is disclosed in U.S. Pat. No. 4,206,726 to John L. Johnson, Jr. issued Jun. 10, 1980. A nozzle is mounted to the engine and includes a first jet and a second jet. The first jet is directed to a central cavity on the underside within a piston and the second jet is directed to a coolant-receiving passage within the piston. The nozzle is formed from an elbow-shaped casting having a passage extending the length of the casting. A pair of plugs are threadedly positioned in each end of the passage. A pair of straight line bores intersect the passage and terminate in exit orifices. To insure that the column of coolant will be highly directionalized, the cross-sectional configuration along the bore's length is identical and its length to diameter ratio at the orifice is in the range of 13:1 to 15:1.
U.S. Pat. No. 2,800,199 to Rudolf Schmidl, issued Jul. 23, 1957 discloses another nozzle arrangement for cooling a piston. In this arrangement, the nozzle includes a cast housing having generally centered passage therein. One end of the passage is closed by a threaded plug and the other end of the passage intersects with a bore. A replaceable nozzle tip is threadedly positioned in one end of the bore and has an orifice therein through which the stream of cooling media exits and is directed to the underside of a piston.
Thus, the geometry within the nozzle to insure efficient flow, reduced turbulences, reduces eddie currents and positioning the proper stream or spray from the nozzle is critical in efficiently cooling the undercrown of the piston assembly.